BOSTON — As David Ortiz stood in front of his locker in the Red Sox clubhouse last night, he was asked how easy it was to dismiss an 8-4 loss to the Indians.

The Sox’ big designated hitter smiled a knowing smile and his team’s double-digit lead in the American League East race all but lit up his eyes.

“We’re playing good. We just lost tonight,” Ortiz said.

Then Ortiz was asked the significance of playing the rival New York Yankees again this weekend with the Red Sox holding a 13½-game division lead. He smiled again and said, “We’re not worried about anybody. Just play the game. It’s not our problem. It’s their problem to try to win some games.”

For the first time this week, the Red Sox last night didn’t receive a sterling effort from a starting pitcher but at this point of the season that didn’t seem to matter very much. The Sox have the final day of May off to rest, play golf or pick up their children from school. They also have reason to celebrate with a whopping 11½-game lead in the American League East in their back pockets. The two months of work spent accumulating that advantage gives the Sox room to dismiss a very shaky outing like the one Daisuke Matsuzaka turned in last night against the Indians.

Dice-K didn’t resemble the rookie flash that’s baffled several opponents with a vast array of offerings so far this season. He was rocked for 12 hits and six runs over just 5 2/3 innings, easily his shakiest outing of the season. The Indians did most of their damage in the fifth and sixth innings when they battered hit up Matsuzaka for six runs on eight hits, with several of his pitches being scalded.

Instead of keeping the Indians guessing as to which pitch he’d throw next, Matsuzaka seemed to rely on his fastball a bit too much and left too many off-speed pitches — like the fat slider Grady Sizemore crushed over the bullpen wall in right for a two-run homer in the sixth — out over the plate.

Boston’s bullpen wasn’t much better. Cleveland pounded out a season-high 18 hits and showed why they’ll be a factor all season long in the A.L. Central.

Now the Red Sox have a chance to begin the third month of the season by supplying another deadly blow to their arch-rivals from New York. The Yankees come to town for a weekend series that some are billing as a potential burial for the boys from Gotham. Indeed, it could be.

The Yanks snapped a five-game nosedive with a 10-5 win last night in Toronto that cut their deficit in the A.L. East to 13½ games. A Red Sox sweep this weekend would bury the Yanks in a 16½ -game hole. The flip side is a Yankee sweep would cut the lead to 10½ and give Derek Jeter, Alex Rodriguez and the newest addition to the pitching staff (Roger Clemens) reason to hope over the next few months.

At this point, the series means a lot more to New York than it does to Boston’s boys of summer. But that doesn’t mean the Red Sox are on cruise control. Take Jason Varitek, for example. Asked last night about the series, the Sox catcher snarled, “Take the lead and throw it out the window. It’s the Yankees and it’ll always be a big series.”

Asked if it bothered him that Clemens wouldn’t make his debut in pinstripes this weekend, Varitek said, “I don’t care what they’re doing. We have to worry about our house.”

However the weekend ends up, the Red Sox clearly have reason to hold all the confidence in the world. Despite Matsuzaka’s shaky outing last night, the team’s starting pitching has been excellent. A deep and talented lineup has racked up the third-most runs in the American League, even with big bopper Manny Ramirez off to a less-than-stellar start. The bullpen has been better than solid, too, with Jonathan Papelbon throwing well and lefty set-up man Hideki Okajima emerging as one of the biggest surprises in baseball.

kmcnamar@projo.com